Efflorescence, commonly known as salt bloom, is the development of white salt deposits that form on the surface of concrete causing a patchy appearance. Aside from the unsightly discolouration and sometimes-crusty texture, efflorescence is typically innocuous.
Primary efflorescence generally occurs as the concrete sets during the hardening phase. Secondary efflorescence occurs as a result of the effects of weathering on the concrete. Lighter coloured concrete will tend to show the deposits to a much lesser degree than dark coloured concrete.
Over time, efflorescence will eventually decrease and become less extensive. Efflorescence formation is generally more obvious during winter but can be recognised all year round, particularly following heavy rain and a fall in temperature. It is also more prevalent in coastal areas such as Sydney.
Efflorescence is caused by the migration of dissolved salts from the inside of the concrete towards the exterior surface. As it reaches the surface, it is exposed to the air and reacts with carbon dioxide causing a white salt to form.
The majority of these dissolvable salts originate from the concrete itself. Calcium hydroxide, also known as "free lime", is the source of efflorescence and is an unavoidable by-product caused by the hydration of the concrete mixture.
Other factors contributing to the presence of these soluble salts may be dirty water, water with a high level of dissolved salt or unwashed or unclean sand. Using too much water when mixing and cleaning up may also lead to efflorescence. Concrete that's been in correctly mixed can have air trapped within that may also lead to efflorescence.
Whilst it's true that efflorescence is a problem as old as the pyramids and that there is no sure fire method to prevent the problem, there are steps that can be taken that will reduce the likelihood of it occurring.
Older concrete that is suffering from rising damp can be treated with an epoxy coating to seal the surface and prevent the salt leaching out. If the concrete is being freshly laid then it's important to ensure your concrete contractor is using additives that will stabilise the mix and reduce the chances of efflorescence occurring in the first instance.
Hills Kerbs uses a unique specially formulated multipurpose concrete additive that's specifically designed to minimise the occurrence of efflorescence and the effects of salt bloom in concrete kerbing. Our exclusive concrete additive also delivers a range of other positive performance enhancing benefits to our garden edging and concrete kerb products, including:
Don’t take risks when hiring a concreter. To ensure your new garden edging is made with premium additives and mixed to the highest standards possible for optimum performance and strength, call Hills Kerbs, Sydney’s leading professional kerbing and concrete contractor.